People born in rural communities in the South, especially in southern Appalachia and the Mississippi Delta, may live shorter and less healthy lives than their counterparts elsewhere in the country, in part due to a high burden ...

Diarrhea caused by Clostridiodes (formerly Clostridium) difficile infections is on the rise among children; one population-based study found a 12.5-fold increase in incidence from 1991 to 2009. For reasons that aren't clear, ...

The human gut microbiome is a complex microbial ecosystem that plays an important role in our health. For example, these microbes—bacteria, viruses, fungi—help regulate metabolism, fend off infections, produce essential ...

More than a quarter of people who regularly meditate have had a 'particularly unpleasant' psychological experience related to the practice, including feelings of fear and distorted emotions, a UCL-led study has found.

A Massachusetts General Hospital (MGH) study has found evidence that children under 3 years old are most the vulnerable to the effects of adversity—experiences including poverty, family and financial instability, and abuse—on ...

A team of researchers from the University of Bristol and AstraZeneca has found what they describe as a link between the "locus of control" (LoC) in adolescents and their use of tobacco and alcohol. In their paper published ...

Attention deficit hyperactivity disorder (ADHD) is one of the most common psychiatric diagnoses among children and adolescents worldwide. The standard of care for ADHD typically includes long-term treatment with stimulants, ...

Early life trauma may affect the structure of the brain in a way that makes clinical depression more likely to be severe and recurrent, according to a two-year observational study of 110 patients published in The Lancet Psychiatry ...

Longitudinal study

A longitudinal study is a correlational research study that involves repeated observations of the same items over long periods of time — often many decades. It is a type of observational study. Longitudinal studies are often used in psychology to study developmental trends across the life span, and in sociology to study life events throughout lifetimes or generations. The reason for this is that unlike cross-sectional studies, longitudinal studies track the same people, and therefore the differences observed in those people are less likely to be the result of cultural differences across generations. Because of this benefit, longitudinal studies make observing changes more accurate and they are applied in various other fields. In medicine, the design is used to uncover predictors of certain diseases. In advertising, the Communicus System, the design is used to identify the changes that advertising has produced in the attitudes and behaviors of those within the target audience who have seen the advertising campaign.

Because longitudinal studies are observational, in the sense that they observe the state of the world without manipulating it, it has been argued that they may have less power to detect causal relationships than do experiments. But because of the repeated observation at the individual level, they have more power than cross-sectional observational studies, by virtue of being able to exclude time-invariant unobserved individual differences, and by virtue of observing the temporal order of events.

Longitudinal studies allow social scientists to distinguish short from long-term phenomena, such as poverty. If the poverty rate is 10% at a point in time, this may mean that 10% of the population are always poor, or that the whole population experiences poverty for 10% of the time. It is not possible to conclude which of these possibilities is the case using one-off cross-sectional studies.

Types of longitudinal studies include cohort studies and panel studies. Cohort studies sample a cohort, defined as a group experiencing some event (typically birth) in a selected time period, and studying them at intervals through time. Panel studies sample a cross-section, and survey it at (usually regular) intervals.

A retrospective study is a longitudinal study that looks back in time. For instance a researcher may look up the medical records of previous years to look for a trend.

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